Synthesis and Characterisation of Transition Metal Complexes of a Novel 1,5‐benzodiazepine‐Functionalised Tertiary Phosphine

• Published in: European journal of inorganic chemistry 2021-06, Vol.2021 (23), p.2274-2280
• Main Authors: Durran, Sean E., Elsegood, Mark R. J., Noble, Thomas A., Smith, Martin B., Gelbrich, Thomas, Hursthouse, Michael B., Light, Mark E.
• Format: Article
• Language: English
• Subjects: 1,5-Benzodiazapines; Benzodiazepines; Coordination compounds; C−H activation; Dichloromethane; Hydrogen bonds; Inorganic chemistry; Late-transition metals; Ligands; Phosphine ligands; Phosphines; Rhodium; Room temperature; Single crystals; Structure elucidation; Synthesis; Transition metal compounds
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.202100236

The one‐step synthesis (44 % isolated yield) of the 1,5‐benzodiazapine functionalised phosphine 1, C31H31N2OP, is reported. Bridge cleavage of {MCl(μ‐Cl)(η5‐Cp*)}2 (M=Ir, Rh) with 2 equiv. of 1 in CH2Cl2 gave the mononuclear compounds [MCl2(η5‐Cp*)(P‐1)] (M=Ir, 2 a; M=Rh, 2 b) in which 1 functions as a P‐monodentate ligand. Rapid C(sp3)−H bond activation, at room temperature, is observed for 2 a leading to the unusual cyclometallated complex [Ir(η5‐Cp*)(P,N,C‐1)]Cl2 3 (or 3‘) bearing an anionic P/Namine/C‐terdentate ligand. Reaction of [Pt(CH3)Cl(η4‐cod)] with one equiv. of 1 led to [Pt(CH3)Cl(P,N‐1)] 4, suggesting that 3 may form via an intermediate IrIII cationic species in which the ligand is P,N‐bound. The IrI complex [IrCl(η4‐cod)(P‐1)] 5 does not, under similar conditions, show any evidence for C−H activation. Single crystal X‐ray studies on 1, 2 a, 2 b, 3, 3‘, 4, and 5 reveal intramolecular N ⋅⋅⋅ H−O H‐bonding in all cases. Mild C(sp3)−H activation of an IrIII phosphine functionalised 1,5‐benzodiazapine affords selectively an unusual cyclometallated piano‐stool complex bearing an anionic P/Namine/C‐terdentate ligand. The facile synthesis of the new functionalised tertiary phosphine, and its coordination chemistry to Ir(I), Ir(III), Rh(III) and Pt(II), are reported.